Di(het)arylaminothiophene derivatives

ABSTRACT

The invention relates to novel 2-(N,N-di(het)arylamino)-thiophene derivatives of formula (I), wherein R 1 , R 2 , R 3 , R 4l and R   5  are, independently each of other, each a monofunctional (het)aryl system and wherein R 1  can also be a bifunctional (het)arylene system, R 3  can also be a group R 8 , except when R 1  is a bifunctional (het)arylene system, R 8  representing chemical bond or a bifunctional (het)arylene system, R 4  can also mean R 10 , R 10  representing a chemical bond or a bifunctional (het)arylene system, or R 4  can be one of the following groups (II) and (I), R 9  representing a chemical bond or a bifunctional (het)arylene system and R 5  can also be H or (IV).

[0001] The invention relates to novel di(het)arylamino-thiophenederivatives, i.e. diarylaminothiophene or dihetarylaminothiophenederivatives (“hetaryl”=“heteroaryl”), and their preparation and use.

[0002] For organic light-emitting diodes (organic LEDs=OLEDs) andorganic photovoltaic components, organic materials which are capable ofelectroluminescence are required. These may be either compounds having asmall molecular size (cf. for example U.S. Pat. No. 4,539,507) which arevaporizable or polymeric materials (cf. for example U.S. Pat. No.5,247,190) which can be processed by spin-coating.

[0003] The synthesis of compounds of said type requires aromaticcoupling reactions. Such reactions, in which halogen-containingcompounds are used, take place in some cases under metal catalysis, forexample according to a Heck reaction or according to a Suzuki reaction(in this context, cf.: “Chem. Commun.”, 1999, pages 1837 to 1838). Here,however, it is scarcely possible completely to remove the metal, such aspalladium (in this context, cf.: “Römpp Chemie-Lexikon”, 9th edition,page 1750). However, metals—and traces of halogen-containingintermediates not completely reacted—act as so-called quenchers, i.e.they quench the electroluminescence in their environment, and theytherefore greatly reduce the efficiency of the materials produced.

[0004] In the case of aromatic coupling corresponding to an Ullmannreaction (in this context, cf.: “Römpp Chemie-Lexikon”, 9th edition,page 4796), the formation of byproducts and of crack products, whicharise owing to high process temperatures, is a major problem. In fact,the purification of the reaction product to an acceptable extent isscarcely possible or not possible at all.

[0005] The invention therefore relates to novel 3,4-substituted2-(N,N-di(het)arylamino)thiophene derivatives of the general structure

[0006] in which the following is applicable:

[0007] R¹, R², R³, R⁴ and R⁵—independently of one another—are each amonofunctional (het)aryl system, i.e. a conjugated carbocyclic orheterocyclic ring system which may also comprise identical or differentring types which are linked or fused on linearly or at angles, it beingpossible for the peripheral hydrogen atoms to be substituted by alkyl,alkoxy, phenoxy, dialkylamino or diphenylamino groups (alkyl=C₁ to C₆);

[0008] R¹ may furthermore be a corresponding bifunctional (het)arylsystem, i.e. a conjugated carbocyclic or heterocyclic ring system whichmay also comprise identical or different ring types linked or fused onlinearly or at angles, it being possible for the peripheral hydrogenatoms to be substituted by alkyl, alkoxy, phenoxy, dialkylamino ordiphenylamino groups (alkyl=C₁ to C₆);

[0009] R³ may furthermore be a group R⁸, except if R¹ is a bifunctional(het)arylene system, R⁸ representing a chemical bond or a bifunctional(het)arylene system;

[0010] R⁴ may furthermore denote R¹⁰, R¹⁰ representing a chemical bondor a bifunctional (het)arylene system, or R⁴ may be one of the followinggroups:

[0011] R⁹ representing a chemical bond or a bifunctional (het)arylenesystem;

[0012] R⁵ may also be H or

[0013]  the following may furthermore be the case:

[0014] R⁴ and R⁵ together form one of the following groups:

[0015] R⁴ and R¹ together form the following group:

[0016] R⁴ and R³ together form the following group:

[0017] R⁵ and R¹ together form the following group:

[0018] R⁵ and R³ together form the following group:

[0019] R⁵, R⁴ and R¹ together form one of the following groups:

[0020] R⁵, R⁴ and R³ together form the following group:

[0021] Y in each case denoting CH or N.

[0022] The preparation of the novel di(het)arylaminothiophenederivatives is carried out by means of a hetaryl cyclization reactionunder mild conditions and without metal catalysts. These compounds cantherefore be prepared in high purity, i.e. the efficiency of thesematerials, in particular the electroluminescence, is not adverselyaffected by impurities which are present in compounds prepared by knownprocesses, for example owing to the catalyst used. A further advantageof these materials consists in improved redox properties adaptable tothe respective purpose, owing to the wide range of possible structureswhich arise from the synthesis principle described in more detail below.This synthesis principle furthermore makes it possible to obtain thenovel materials without problems, also in the form of oligomer andpolymer structures, i.e. to prepare oligo- and polyaminothiophenederivatives.

[0023] The synthesis of the novel compounds requires in some casesprecursors which have not been known to date. However, these precursorsare obtainable—from commercially available starting materials—invirtually quantitative yield.

[0024] The following is applicable here:

[0025] R¹, R², R³, R⁴ and R⁵ have the abovementioned meaning;

[0026] R⁶ and R⁷—independently of one another—are each a monofunctional(het)aryl system, i.e. a conjugated carbocyclic or heterocyclic ringsystem, which may also comprise identical or different ring types linkedor fused on linearly or at angles, it being possible for the peripheralhydrogen atoms to be substituted by alkyl, alkoxy, phenoxy, dialkylaminoor diphenylamino groups (alkyl=C₁ to C₆);

[0027] R⁶ may furthermore be the group R⁹, the compound V carrying, atthe free bond, a group —CO—CH₂X where X=halogen, preferably Cl, Br or I,

[0028] or R⁶ may be a group —C(CO—CH₂X)₃.

[0029] The first stage of the synthesis of the thiophene derivativescomprises the reaction of a secondary amine I with an acyl halide II togive a carboxamide (acid amide) III. The reaction is carried out in asuitable solvent, preferably dioxane, at elevated temperature,preferably in the region of the boiling point of the solvent, underinert gas. The reaction is stopped when the hydrohalide (hydrogenhalide) formed as the byproduct is removed by the inert gas stream orwhen no more amine is detectable, for example by checking by thin-layerchromatography.

[0030] The acid amide III is then converted into a thiocarboxamide(thioamide) IV in a second stage. This is advantageously effected bymeans of the so-called Lawesson reagent, a reagent which acts in thehomogeneous phase for introducing sulfur into carbonyl compounds (inthis context, cf.: “Römpp Chemie-Lexikon”, 9th edition, page 2464), in asuitable solvent, preferably diglycol diethyl ether, at elevatedtemperature, preferably at about 100° C.; duration: several hours, ingeneral about 6 h. However, the sulfur can also be introduced in theheterogeneous phase, for example by means of phosphorus pentasulfite.

[0031] In a third stage, the thioamide IV—depending on the substitutionpattern (cf. IVa to IVc below)—is converted into a semiconducting3,4-substituted 2-(N,N-di(het)arylaimino)thiophene derivative VI byreaction with an α-haloacyl compound V in a suitable solvent, preferablymethylene chloride, dichloroethane, acetic anhydride, dimethylformamideor tetrahydrofuran, depending on the substitution pattern of the acylcompound (cf. Va to Vd below). This is effected by a primaryS-alkylation and a subsequent cyclization (ring closure reaction) andaromatization. The cyclization can be accelerated by adding adeprotonating agent, preferably triethylamine.

[0032] Thiophene derivatives VI which are unsubstituted in the5-position, i.e. R⁵=H, can be converted by oxidative coupling intodimeric or polymeric derivatives VI (cf. VIg, h, i, n, r, s, t, v and zbelow), which are likewise semiconductor materials. The oxidativecoupling is effected in a suitable solvent, preferably drytetrahydrofuran, by oxidizing agents known per se, preferably byoxidation of the respective thiophene derivative, converted into thelithium compound by means of butyllithium, with copper(II) chloride orby electrooxidation on a conductive substrate, for example on a glassplate coated with ITO (ITO=indium tin oxide).

[0033] By means of halogenated 1,2-diketones (cf. Vd/d below) —as theα-haloacyl compound—thiophene derivatives VI which are prepared from thethiocarboxamides IV and are unsubstituted in the 5,5′-position andlinked in the 4,4′-position (cf. VIw and VIx below) can be converted,with orthoformic esters or with nitrous acid, which is generated, forexample, from sodium nitrite or isoamyl nitrite, into correspondingcationic hole transport materials (cf. VI/1 and VI/2 below) which areanalogous to the known polythiophenes and polyanilines in their propertyas organic conductors.

[0034] The structural formulae of a relatively large number of the novelthiophene derivatives—together with the direct starting materials—areshown below in table form. Organically semiconducting products from thecombinations of thiocarboxamides IV and □-haloacyl compounds V and theiroxidation products and conductive cationic structures

IVa Oxidation

IVb

IVc Va

VIa VIb

VIc Vb

VId VIe

VIf Vc

VIg VIh

VIi R⁹ = arylene system- not 1,2-linked Vd/a

VIk VIn

VIl VIm

R⁹ = arylene system- VIo not 1,2-linked Vd/b

VIp VIq Oxidation

VIr

VIs VIt

R⁶ = —C(CO—CH₂X)₃ Vd/c

VIu VIv

R⁹ = chemical bond VIw Vd/d

VIz VIx

a) CH(OR¹¹)₃b) HNO₂ VIy

VI/1 VI/2

[0035] R¹¹ is an alkyl radical having 1 to 5 C atoms, Z⁻ is any desiredanion, preferably a polystyrene-sulfonate or another organic sulfonate,

[0036] n denotes in each case an integer from 2 to 100.

[0037] The thiophene derivatives according to the invention of the typeVI are all suitable materials for the synthesis of organiclight-emitting diodes (OLEDS) and organic photovoltaic components orcells. They can be used both in hole transport layers or layer cascadesand in emitter and electron transport layers. The respective layerposition in OLEDs is determined in particular by the (het)aryl or(het)arylene members; the more of these members have a π-electrondeficiency, i.e. so-called π-deficient aromatics, the more suitable arethe thiophene derivatives as emitter and electron transport materials.

[0038] The following types of compounds are particularly preferred:

[0039] VIb, VIc, VIe, VIf, VIg, VIh, VIi and VIk;

[0040] VIr;

[0041] VIv;

[0042] VI/1 and VI/2.

[0043] Both OLED materials which are suitable as vaporizable compoundsfor so-called “small molecule devices” and polymer materials processibleby spin-coating and intended for so-called “polymer devices” can berealized via the synthesis route described; the nonpolymeric materialscan likewise be processed by spin-coating. Owing to the common parentstructure of all materials, corresponding copolymers having tailoredelectronic properties can also advantageously be prepared. It isfurthermore possible to realize the electronic properties required forthe respective intended use by mixtures of corresponding materialswhich—owing to the structural similarity—are very compatible with oneanother. Materials tailored in this manner therefore permit asingle-layer structure of OLEDs, which is very advantageous. Glasstransition temperatures of the charge transport and emitter materialsprepared in the manner described, which are very high compared withknown carbocyclic charge transport materials and are in general about 50to 100° C. higher than those of the analogous carbocyclic compounds, arealso remarkable.

[0044] The invention is to be explained in more detail with reference toexemplary embodiments.

EXAMPLE 1

[0045] Synthesis of Carboxamides III

[0046] In a 2 l three-necked flask having a reflux condenser, magneticstirrer, dropping funnel and inert gas flow-through, in each case 1 molof a secondary amine I is dissolved in 600 ml of dioxane. The acylhalide II required in each case is then added dropwise in an equivalentamount. The reaction mixture is then refluxed until the total amount ofthe hydrohalide formed in the reaction has been removed by the inert gasstream. The end of the reaction can additionally be detected by checkingby means of thin-layer chromatography. The reaction solution is thencooled and is stirred into at least twice the amount of water. In mostcases an oil separates out, which solidifies after a few hours. Theaqueous phase is separated off and the crude product is recrystallizedfrom ethanol. The yield is at least 90% in each case.

[0047] For example, N,N-diphenyl-2-phenylacetamide (m.p.: 71-72° C.) isprepared in this manner from diphenylamine and 2-phenylacetyl chloride.

EXAMPLE 2

[0048] Synthesis of Thiocarboxamides IV

[0049] 0.5 mol of the respective carboxamide III and the equivalentamount of Lawesson reagent (prepared from anisole and phosphoruspentasulfide) are suspended in 750 ml of diglycol diethyl ether in areflux apparatus with inert gas flow-through, and stirring is thencarried out for 6 h at 100° C. A clear solution forms, from which thereaction product crystallizes out at room temperature in some cases. Inorder to isolate. the product completely, the reaction mixture isstirred into twice the amount of water, and the oily phase which oftenforms is then allowed to crystallize, Thereafter, the product isseparated from the aqueous phase and recrystallized from methanol. Theyield is at least 90% in each case.

[0050] For example, the thiocarboxamide IVb (R¹=1,4-phenylene andR²=R³=phenyl) (m.p.: 225-227° C., M⁺=528) is prepared in this mannerfrom the carboxamide III (R¹=1,4-phenylene and R²=R³=phenyl).

EXAMPLE 3

[0051] Synthesis of Thiophene Derivatives VI

[0052] In a flask which is provided with a stirrer and reflux condenser,0.1 mol of the respective thiocarboxamide IV are dissolved, togetherwith the equivalent amount of an α-haloacyl compound V, in 200 ml ofDMF, after which heating to 100° C. is carried out for 1 h. 0.1 mol oftriethylamine are then added and heating is carried out for a further 30min. After cooling, the resulting thiophene derivative is isolated byprecipitation with ethanol, in some cases also with water, andfiltration with suction. The crude product is purified by dissolving inTHF and precipitating with ethanol. The yield is between 60 and 80% ineach case.

[0053] For example, the thiophene derivative VIb (R¹=1,4-phenylene andR²=R³=R⁴=R⁵=phenyl) (m.p.: 318° C., T_(g)=275° C., M⁺=880) is preparedin this manner from the thiocarboxamide IVb (R¹=1,4 phenylene andR²=R³=phenyl) and desyl chloride (α-chloro-α-phenylaceto-phenone), andthe thiophene derivative VIb (R¹=1,4-biphenylene and R²=R³=R⁴=R⁵=phenyl)(m.p.: 285° C. ° C., T_(g)=270° C., M⁺=956) is prepared in this mannerfrom the thiocarboxamide IVb (R¹=1,4 biphenylene and R²=R³=phenyl) anddesyl chloride (α-chloro-α-phenylacetophenone).

[0054] The following procedure is used for the preparation of polymericthiophene derivatives VI, for example VIh (R¹=1,4-phenylene andR²=R³=R⁴=phenyl):

[0055]¹H-NMR: a=6.90 ppm (d), b=7.10 ppm (t), (DMF-D₆)

[0056] In a flask which is provided with stirrer and reflux condenser,0.1 mol of thiocarboxamide IVb (R¹=1,4-phenylene, R²=R³=phenyl) aredissolved, together with 0.1 mol of dimeric phenacyl bromide Vc(R²=phenyl), in 200 ml of DMF, after which heating to 100° C. is carriedout for 1 h. For blocking terminal groups, a monofunctional vinylogousthioamide and a monofunctional acyl halide are then added in succession,in the present case first 0.01 mol of N,N-diphenyl-2-phenylthioacetamideand, after 60 min, 0.01 mol of phenacyl bromide. After a further 60 min,0.1 mol of triethylamine are added and, after a further 15 min, themixture is allowed to cool, the polymeric thiophene derivative formedbeing precipitated. The further working-up is carried out in the mannerdescribed above; yield: about 80%.

EXAMPLE 4

[0057] Synthesis of Dimeric or Polymeric Thiophene Derivatives VI (byOxidative Coupling)

[0058] In a flask which is provided with a reflux condenser, stirrer,solids metering means and inert gas flow-through, 0.01 mol of athiophene derivative VI unsubstituted in the 5-position are dissolved in100 ml of dried THF. Cooling to −60° C. is effected, and then 0.015 molof butyllithium are added. Thereafter, the cooling is removed and thereaction mixture is allowed to thaw at up to −10° C. 0.011 mol ofcopper(II) chloride are then added by the solids metering means, andfurther heating is then carried out to 40° C. The reaction is stoppedafter 30 min by precipitating the product with water (in the case ofpolymers, with methanol with the addition of 10% of water) and is thenfiltered off with suction. The product is purified by repeateddissolution in THF and precipitation with methanol. Nonpolymericcompounds can also be purified by sublimation.

[0059] For example, the dimeric thiophene derivative VIg(R¹=R²=R³=R⁴=phenyl) (m.p.: 255-285° C., M⁺=804) is prepared in thismanner from 2-diphenylamino-3,4-diphenylthiophene VId.

EXAMPLE 5

[0060] Synthesis of Thiophene Derivatives VI in the Form of CationicallyConductive Materials (Y=CH)

[0061] In a beaker, 0.01 mol of a dimeric thiophene derivative VI linkedin the 4,4′-position and unsubstituted in the 5,5′-position aredissolved in 100 ml of DMF, and 0.015 mol of triethyl orthoformate areadded. After the addition of 0.01 mol of perchloric acid and heating toabout 100° C., a colored salt absorbing in the long-wave range forms,which salt, after the addition of ethanol and possibly a little ether,is precipitated and then filtered off with suction. By reacting theperchlorate dye with a solution of sodium polysytrenesulfonate, anaqueous solution of the respective cationically conductive material isobtained as polystyrene-sulfonate; this solution can be processed byspin-coating.

[0062]¹H-NMR: a=7.20 ppm (s), b=7.60 ppm (t), c=7.40 ppm (t) (DMSO-D₆)λ_(max)=687 nm

[0063] For example, the thiophene derivative VI/1 (R¹=R²=R³=phenyl andY=CH) (M⁺=663) is prepared in this manner from the thiophene derivativeVIw (R¹=R²=R³=phenyl) and triethyl orthoformate in the presence ofperchloric acid.

EXAMPLE 6

[0064] Synthesis of Thiophene Derivatives VI in the Form of CationicallyConductive Materials (Y=N)

[0065] In a beaker, 0.01 mol of a dimeric thiophene derivative VI linkedin the 4,4′-position and unsubstituted in the 5,51′-position aredissolved in 100 ml of THF, and 0.015 mol of isoamyl nitrate is added.After the addition of 0.01 mol of perchloric acid with cooling andsubsequent heating to about 50° C., a colored salt absorbing in thelong-wave range forms, which salt, after the addition of ethanol andpossibly a little ether, is precipitated and then filtered off withsuction. By reacting the perchlorate dye with a solution of sodiumpolystyrenesulfonate, an aqueous solution of the respective cationicallyconductive material is obtained as polystyrenesulfonate; this solutioncan be processed by spin-coating.

[0066]¹H-NMR: a=7.65 ppm (t), b=7.55 ppm (t), (DMSo-D₆) λ_(max)=750 nm

[0067] For example, the thiophene derivative VI/1 (R¹=R²=R³=phenyl andY=N) (M⁺=664) is prepared in this manner from the thiophene derivativeVIw (R¹=R²=R³=phenyl) and isoamyl nitrite in the presence of perchloricacid.

1. A 2-(N,N-di(het)arylamino)thiophene derivative of the structure

in which the following is applicable: R¹, R², R³, R⁴ andR⁵—independently of one another —are each a monofunctional (het)arylsystem, in the form of a conjugated carbocyclic or heterocyclic ringsystem which may also comprise identical or different ring types whichare linked or fused on linearly or at angles, it being possible for theperipheral hydrogen atoms to be substituted by alkyl, alkoxy, phenoxy,dialkylamino or diphenylamino groups (alkyl=C₁ to C₆); R¹ mayfurthermore be a corresponding bifunctional (het)aryl system, R³ mayfurthermore be a group R⁸, except if R¹ is a bifunctional (het)arylenesystem, R⁸ representing a chemical bond or a bifunctional (het)arylenesystem; R⁴ may furthermore denote R¹⁰, R¹⁰ representing a chemical bondor a bifunctional (het)arylene system, or R⁴ may be one of the followinggroups:

R⁹ representing a chemical bond or a bifunctional (het)arylene system;R⁵ may also be H or

 the following may furthermore be the case: R⁴ and R⁵ together form oneof the following groups:

R⁴ and R¹ together form the following group:

R⁴ and R³ together form the following group:

R⁵ and R¹ together form the following group:

R⁵ and R³ together form the following group:

R⁵, R⁴ and R¹ together form one of the following groups:

R⁵, R⁴ and R³ together form the following group:

Y in each case denoting CH or N.
 2. The thiophene derivative as claimedin claim 1, of the following structure:


3. The thiophene derivative as claimed in claim 1, of the followingstructure:


4. The thiophene derivative as claimed in claim 1, of the followingstructure:


5. The thiophene derivative as claimed in claim 1, of the followingstructure:

Z⁻ denoting an anion and n denoting an integer from 2 to
 100. 6. Aprocess for the preparation of a thiophene derivatives as claimed inclaim 1, characterized by the following steps; (a) reaction of asecondary amine with an acyl halide to give a carboxamide; (b)conversion of the carboxamide into a thiocarboxamide; (c) reaction ofthe thiocarboxamide with an α-haloacyl compound to give a2-(N,N-di(het)arylamino)thiophene derivative.
 7. The process as claimedin claim 6, characterized in that the thiophene derivative is convertedoxidatively into a dimer or polymer.
 8. The process as claimed in claim6, characterized in that the thiophene derivative is converted by meansof an orthoformic ester or nitrous acid into a polythiophene derivative.9. The use of the thiophene derivatives as claimed in any of claims 1 to5 in organic light-emitting diodes.
 10. The use of thiophene derivativesas claimed in any of claims 1 to 5 in organic photovoltaic components.